Generally, to date there have been two coring type, excisional breast biopsy devices developed and marketed. These devices are described in the following U.S. Pat. Nos. 5,111,828; 5,197,484; 5,353,804; 6,080,113; 6,267,732; 6,383,145; 6,551,253; 5,782,775; 5,817,034; 5,857,982; 6,036,657; 6,077,231; 6,165,137; and 6,213,957, all of which are hereby incorporated by reference.
These devices were originally developed for use with stereotactic imaging equipment. Generally, these devices use the same basic technology. The device disclosed in the '253 patent is exemplary. The biopsy device includes a localization needle with a guide wire preloaded into the device. The localization needle and guide wire are used to locate and localize the target area. The methodology of their usage can be summarized as follows:                1. Localize the target area with needle/wire hook;        2. Translate device up to the target area using a bladed stylet;        3. Core out the target specimen using a bladed cannula; and        4. Transect the tissue using a garrote wire to release the specimen.        
The device can either by a handheld device or may be a fixed device. The below more detailed description of the method of using a prior art device is described with respect to a handheld device.
First, a localization needle is placed at the center of the target tissue. A localization wire is used to fix the handheld device to the tissue. After the localization wire is deployed, a stylet is manually advanced to a point just proximal of the target.
One problem associated with the current device is that the localization hook has very little holding power.
Another issue related to the prior art devices is the potential of the stylet to push and/or compress, i.e., the tissue in front of the stylet, i.e., “snowplow”.
After the stylet reaches the target tissue, the cannula is manually advanced over the target tissue. With the cannula advanced over the target tissue, a mechanism, such as a garrote wire is activated to sever the target tissue from the breast. With the target tissue severed from the breast, the device, along with the target tissue with the cannula, may be removed.
Generally, these prior art devices are purely mechanical devices, i.e., in other words, the coring cannula is advanced by hand. The surgeon or user rotates a knob that activates a gear system to rotate and advances the coring cannula. This results in a relatively slow, intermittent advance of the cannula due to the start/stop motion of the surgeon. The start/stop motion can increase patient discomfort, as well as produce an undesirable irregular specimen shape.
As discussed above, once the cannula has been advanced over the target tissue, a garrote wire may be used to cut the sample tissue (which is inside the cannula) from the breast so that it may be removed. The garrote wire has several limitations. Typically, the garrote wire traverse (at least partially) along the length of the device, then is bent at a 90 degree angle, after which it encircles an inner surface of the coring cannula. The right angle in the garrote wire results in requiring a large amount of force to pull on the garrote wire to transect the tissue sample. Additionally, the garrote wire is generally located a distance behind the cutting edge of the coring cannula. This results in a core of tissue which is cored by the coring cannula, which is not transected by the garrote wire, and thus remains in the breast. Furthermore, the garrote wire may tear the tissue rather than cutting the tissue. Additionally, dense tissue can be pushed aside rather than cut.
Another issue related to prior art designs is the size of the cutting edge of the cannula with respect to the stylet. Prior to entry of the device into the breast, a skin incision is made using a scalpel. This incision is generally just slightly wider than the diameter of the cannula. Once the incision is made, the stylet is advanced in the breast, up to the point where the coring blade is ready to enter the incision. At this point, the surgeon will use nerve hooks to grab the skin and open the incision to allow the cutting edge of the cannula to enter the breast. However, the process of using the nerve hooks to grab the skin to make the incision wider can be cumbersome and inefficient and can cause patient discomfort.
The current devices use a stylet with integral cutting blades. The flat stylet blades are fixed to the stylet which may result in several adverse conditions. First, the close proximity of the cutting edge of the stylet blades to the ramp or stylet tip results in the pushing or compression or other inadvertent movement of the tissue by the stylet. The prior designs also results in a fixed minimal proximal margin equal to the length of the stylet system.
The present invention is aimed at one or more of the problems identified above.